With the rapid growth of mobile communications and the enormous development of technology, the world is evolving towards a network society with full connectivity. That is, anyone or anything can obtain information and share data anytime and anywhere. It is expected that, by 2020, there will be 50 billion of interconnected devices, among which only 10 billion will be mobile phones and tablet computers, while others are machines that do not interact with human, but with each other. Hence, there is a topic worth comprehensive research regarding how to design the system to support a huge number of machine communication devices.
In the Long Term Evolution (LTE) standard in the 3rd Generation Partner Project (3GPP), such machine-to-machine communication is referred to as Machine Type Communication (MTC). The MTC is a data communication service without human involvement. A large-scale deployment of MTC UEs can be applied to various fields such as security, tracking, payment, measurement, consumer electronics, and in particular to applications such as video surveillance, supply chain tracking, intelligent metering and remote monitoring. The MTC requires low power consumption and supports low data transmission rate and low mobility. Currently, the LTE system is mainly designed for Human-to-Human (H2H) communication services. Hence, in order to achieve the scale benefit and application prospect of the MTC services, it is important for the LTE network to support the MTC devices to operate at low cost.
Further, some MTC devices are mounted in basements of residential buildings or locations protected by insulating films, metal windows or thick walls of traditional buildings. These devices will suffer significantly higher penetration loss in air interface than conventional device terminals, such as mobile phones and tablets, in the LTE network. The 3GGP has started researches on solution designs and performance evaluations for MTC devices with a 20 dB of additional coverage enhancement. It is to be noted that an MTC device located in an area with poor network coverage has a very low data transmission rate, a very loose delay requirement and a limited mobility. For these MTC characteristics, some signaling and/or channels of the LTE network can be further optimized to better support the MTC services.
For this purpose, in the 3GPP RAN #64 meetings in June, 2014, a new work item for Rel-13 has been proposed for the low complexity and enhanced coverage MTC (see non-patent document: RP-140990, New Work Item on Even Lower Complexity and Enhanced Coverage LTE UE for MTC, Ericsson, NSN). In the description of this work item, the LTE Rel-13 system shall allow MTC UEs supporting 1.4 MHz RF bandwidth in UL/DL (referred to as narrowband MTC UE) to operate over any system bandwidth (e.g., 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz, etc.). In the existing LTE system, an LTE UE can obtain a start Orthogonal Frequency Division Multiplexing (OFDM) symbol of a Physical Downlink Shared Channel (PDSCH) or Enhanced Physical Downlink Control Channel (EPDCCH) from a broadband Physical Control Format Indicator Channel (PCFICH), so as to decode the corresponding PDSCH or EPDCCH. However, a narrowband MTC UE cannot read the broadband PDFICH information. Accordingly, in accordance with the existing LTE standard specifications, a narrowband MTC UE cannot obtain a start OFDM symbol of PDSCH or EPDCCH from PCFICH, and thus cannot decode the corresponding PDSCH or EPDCCH.
There is thus a need for a new solution for a narrowband MTC UE to obtain a start OFDM symbol of PDSCH or EPDCCH.